Field of the Invention
This invention concerns a system for determining the movement properties of at least one vehicle guided along a section (area of transportation comprising several guiding tracks) appropriate for a signaling control of tracks.
As a vehicle, one must understand public transit means such as bus, trolleybus, tramway, subway, train or train units, etc. In particular, units of automatic trains with guiding control (technique also commonly called “CBTC”=“communication based train control”) are aimed at by the invention. These generally comprise vehicles communicating with on-board guiding equipments and (remote-)controlled by ground automatic devices (signalling, central calculator, etc). An example of achievement of such vehicles is known with, among others, registered brands like VAL, AIRVAL, CITYVAL, NEOVAL for which units of trains comprise at least one traction wheel/roller-based device on a guiding rail longitudinally central on a train track and side pneumatic tired wheels, carrying said units on longitudinal concrete-strips on each side of the track.
First, determining the presence properties of a vehicle guided along a section is known under several forms:    a) The traditional solution, which applies to tracks made of two iron rails, consists in installing a “circuit of track” (also in abbreviated form under the diminutive “CoT” afterwards) on each (track of) section: said CoT is made up of an electrical conductor component on-board and electrically connecting the two rails (for example with a signal transmitter-receiver to the section ends) and enables to know the state of occupancy of the section. Generally, the CoT for example can be installed through an iron axle. If this electrical conductor establishes a short circuit between the rails on a section, the CoT of the section is in “off” state and the section is declared occupied by the vehicle. If no short circuit is detected, the CoT is in “on” state and the section is free of vehicle.
When one or several trains are present on the section, each axle thus establishes a short circuit between the two rails, which maintains the CoT in “off” state. As soon as all the axles of the present train or of the present trains have left the section, said section switches to the free state whatever the sequence of arrival or of departure of the trains is. So the CoT does not give the exact number (greater than 1) of vehicles present on a section.
However, safety is nevertheless ensured insofar as almost all the failures of a CoT have the same effect as a short circuit between the rails: the CoT indeed stays in “off” state in case of a failure.
The main drawback of CoT lies also in their high cost.    b) Another solution is the following: when the tracks are not made up of rails (conductors), for example for most subways and tramways equipped with pneumatic tired wheels, other solutions exist and are used:            For systems of CBTC type, each train (or vehicle) is equipped of a calculator, positions itself continuously on the network and transmits permanently its position to a ground calculator or to ground calculators that determine(s) the state of each section. “Negative detectors” (luminous or ultrasound-emitting fences for example) placed at the borders of the system enable to safely detect the arrival of a “mute” train in the network.        Devices located under the trains permanently emit a fixed frequency signal that is picked up by ground receivers associated with receiving loops (antennas) located in the track. Said devices can be associated with negative fences placed in specific points. A ground calculator or ground calculators, connected to the receivers, determine(s) the state of occupancy of each section according to the detection or not of a signal by each receiver. Safety is so ensured either by redundancy of the emitters and of the receivers, or, if the receiving loops cover continuously all the tracks, by controlling that each train emits continuously and by forbidding the arrival of a train in a section already occupied.        
In those two last cases (a and b), if the trains do unexpected or non authorized movements (in particular backward movements or the penetration of a train in a section already occupied), the concerned sections stay frequently and inevitably in the “occupied” state even if there is no train in it. This is very disadvantageous to reach a high efficiency of management and of automated manoeuvres of the vehicles.    c) A document US 2004/0030466 A1 (“train registry overlay system”) finally describes a method for determining presence properties of a vehicle guided along a section. To ensure a backup (save procedure) in case of failure to the CBTC systems without using any CoT because of its cost, a transponder fixed on each vehicle/unit of trains contains an identifier. Trans-ponder readers placed along the tracks extract these identifiers while the trains go past and pass them on to a ground calculator which uses them to determine the occupancy of the tracks.
Safety can be increased by a redundancy of the on-board transponders, of the transponder readers and of the calculators.
However, if this device indeed enables to identify all the trains present in the CBTC system, it does not enable to determine the movement properties of a vehicle, in particular if said vehicle goes in or goes out of a section. In other words, a set transponder/reader cannot deliver a vehicle moving direction. Furthermore, the intrinsic orientation of the vehicle (its front and its rear) in comparison with the track stays unknown too. This aspect is also disadvantageous from an information point of view regarding the CBTC automatisms, in particular to determine the moving direction of the vehicle in comparison with the track, while according to the topology of the track, during its running, it has the possibility to turn around.
In particular, if a vehicle has not been yet identified, it is not possible to know, during its going past a first transponder located on a border between a first and a second section, if it goes out of the first section and goes in the second section or the reverse.
Likewise, if a vehicle already identified stops with its transponder located in front of the transponder reader, it is not possible to determine, when it restarts, if it is going towards a section located upstream of the transponder or towards a section located downstream of the transponder: no one of the two can then be “freed”, in the sense that automatic protections forbid another vehicle to access the section free in reality. These lines-blocked highly penalize the traffic of trains.